Electric discharge apparatus



Feb. 11, 1936. J. w. DAWSON 2,030,100

ELECTRIC DISCHARGE APPARATUS Filed May 11, 1954 Phase Shifterd J Q I 79INVENTOR WITNESSES John W. Dawson Ritua Feb; 11,193

PATENT OFFICE 2.030.100 anaemic mscnaacn maaa'rns John W. Dawson,Wilkinsburg, Pa... alsignor to Westinghouse Electric a ManufacturingCompa y, East Pennsylvania.

Pittsburgh, Pa., a corporation of Application May 11,1934, Serial No.725,107

-- 11 Claims. (01. 175-363) My invention relates to electric dischargeapparatus and has particular relation to apparatus for controlling thesupply of power of a load which is to be continuously varied from onevalue to another.

The invention has particular applicability in the theater switchboardart. In theaters, it is customarily desirable to vary both the stage andauditorium illumination as the scenes on the stage or screen change. Thevariation must necessarily be continuous from one value to another andit is essential that no time be lost in producing the change. 1

Accordingly, the practice has been in accordance with the teaching ofthe prior art to provide a plurality of pre-set voltage-dividers. Thesevoltage-dividers are adjusted to the'desired values before theperformance. They are connected to each other through what may bedesignated as a diflerential voltage-divider the windings of which haveconsiderably higher resistance than the windings of the pro-setvoltage-dividers. The latter voltage-divider is in turn coupled to anamplifier system of one type or another and the operation of theamplifiersystem is controlled in such manner by the differentialvoltage-divider that when the latter is varied, the output illumi- -ofthe electric discharge device is varied and,

therefore, the illumination is varied.

In the following discussion, I shall regard one of the principalelectrodes of the electric dis charge device utilized in the system asthe reference point of potential. Where an electric discharge device ofthe type having a cathode is utilized as is the preferred practice) thecathode will be taken as the reference. The potential impressed betweenthe anode and the cathode, or between the principal electrodes, where acathode is not incorporated or where two cathodes are incorporatedinstead of an anode and a cathode, I shall designate as the principalpotential. The potential impressed between the control electrode and thereference point will be designated as the control potential.

The voltage-divider system discussed hereinabove lends itselfparticularly to the controlling of the output of an electric dischargedevice by 5 variation of the magnitude of the control po-' tentialrelative to the principal potential. For

a number of reasons, which need not be discussed here, it is desirablethat the output of the electrlc discharge device be controlled byshifting the phase of the control potential relative to the principalpotential rather than by varying the magnitude.

It is accordingly an object ofmy invention to provide a system of thetype incorporating an electric discharge device having a controlelectrode and a plurality of principal electrodes for controlling thesupply of current to a load wherein a voltage-divider shall be utilizedto provide the necessary variations and the voltage-divider shall be socoupled to the other elements appurtenant to the discharge device thatthe output of the discharge device shall be varied by shifting the phaseof the control potential applied thereto relative to the principalpotential.

A further object of my invention is to provide simple and tractableapparatus for shifting the phase of the control potential relative tothe principal potential of, an electric discharge device to control thesupply of current therethrough to a load.

An additional object of my invention is to provide apparatusincorporating an electric discharge device having a cathode of the typewhich is to be heated to a predetermined temperature before it cansupply current without deteriorating; wherein the cathode. shall beprotected against premature supply current.

An incidental object of my invention is to provide a phase shiftingsystem whereby it shall be possible to shift the phase of a potentialsupply through a complete angle of 18024;

More concisely stated, it is object of my invention to provide simpleand inexpensive apparatus for continuously controlling the supply ofpower'to a variable load by utilizing an electric discharge device andby shifting the control potential of the device relative to theprincipal potential thereof. g

According to my invention, I provide a system so in which the controlpotential consists of a component out of phase with the principalpotential and a component composed of two superposed component elementsone in opposite phase to the the principal potential. The latter elementis provided by a variable voltage-divider system of the type utilized inthe theater switchboard art. As the supply of this element is varied,the phase relationship of the net control potential relative to theprincipal potential may be varied in any desired manner.

If the electric discharge device utilized is of the hot cathode type,the cathode may be protected from deterioration by the prematureapplication of such potential as will cause current to be transmittedthrough the discharge device by delaying the application of the variableinphase component element which is superposed on the opposite-phaseelement. As long as the opposite-phase element alone is applied, thecontrol potential supplied to the discharge device is so related to theprincipal potential that the discharge device passes only a smallcurrent and in consequence thereof, the cathode is not deteriorated.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and its method ofoperation, together with additional objects and advantages thereof, willbest be understood from the following description of speclflcembodiments when read in connection with the accompanying drawing, inwhich Figure 1 is a diagrammatic view showing the preferred embodimentof my invention;

Fig. 2 is a diagrammatic view of a salient feature of a modification ofmyinvention;

Fig. 3 is a vector diagram illustrating the functioning of the apparatusshown in Fig. l, and

Fig. 4 is a vector diagram illustrating the functioning of the apparatusshown in Fig. 2.

The apparatus shown in Fig. 1 comprises an electric discharge device Ihaving a control electrode 3, an anode 5 and a cathode I. In thepreferred practice of my invention, the electric discharge device is ofthe gas filled type and the cathode is of the filamentary type andpreferably consists of a metal such as nickel or an alloy of nickelcoated with an oxide of an alkaline earth metal. If current istransmitted by the discharge device before the cathode attains apredetermined temperature, the cathode is deteriorated by positive ionbombardment and consequently it is essential to eliminate prematuretransmission of current through the device.

It is apparent that electric discharge devices of other types may beutilized in the practice of my invention. For example, a mercury pooldevice of the Ignitron type or a, high vacuum device are possibilities.At times it may also be desirable to utilize a symmetrically conductivedischarge device rather than the asymmetrically conductive device Iwhich is utilized in the apparatus shown in Fig. 1. I

The discharge device I is supplied with power from a secondary section 9of a transformer it, one terminal l3 of which is connected to thecathode I and the other terminal l5 of which is connected to the anode 5through the saturating winding ll of a saturable-core reactor "l9 andthrough a variable resistor 2|. The load 23 is supplied with powerthrough the output windings 25 of the reactor I! in the usual manner. Asthe current through the discharge device l is carried, the saturation ofthe reactor I9 is varied and consequently, the impedance in series withthe load 23 is varied. The current supplied to the load 28 may thus becontrolled by controlling the output of the discharge device I.

To make certain that the current through the saturating winding ll ofthe reactor I9 is continuous. a rectifier 21 s connected acrossthe'winding, the anode 22 of the rectifier being connected to the anode i ofthe discharge device I through the variable'resistor 2| and the cathode3| of the rectifier being connected to the lower terminal I! of thesecondary section 9. The rectifler 21 functions to maintain the currentin the saturating winding during the intervals during which it is notsupplied through the discharge device. It is apparent that the rectifier21 may be of any suitable type. It may be of the hot cathode gas filledor high vacuum type, or of the mercury pool type'or again of thecoldcathode typ Since my invention is particularly applicable to theaterlighting, the load 23 is shown as a system of illuminating units. Loadsof other 7 types may of course be applied.

The control potentlalsupplied to the discharge device I is composed ofseveral components. One component is supplied through a r phase-shiftingsystem 32 from another secondary section 35 of the power supplytransformer II and is at a phase angle substantially different fromrelative to the principal potential. An-

other component is in opposite phase to the principal potential and issupplied by still another secondary section 31. One terminal tap it andan intermediate tap ll of a voltagedivider 43 are connected to theterminals of the secondary section 21.

The potential output of the voltage-divider I3 is supplied between thecontrol electrode 3 and the cathode 1- through a transformer 45, one terminal of the primary ll of which is connected to a movable contact 49 ofthe voltage-divider 43.-

while the other terminal is connected to another movable contact II 01the voltage-divider. The secondary 53 of the transformer 41 is connectedin series with the output circuit of the phaseshifter 23.

The functioning of the system is illustrated net control potential willbe represented by the broken line vector 6! which it will be noted isalmost in opposite phase to the principal potential vector 55. As longas the broken line vector 6| represents the'control potential suppliedto the discharge device I, the current output of the the device iscomparatively small and the cathode l is protected from deterioration.

An in-phase component of control potential is super-imposed on theopposite phase component between the remaining terminal tap 63 and theintermediate tap ll of the voltage-divider l3 and through a pre-setvoltage-divider system 65. In the pre-set voltage-divider system, aplurality of pre-set voltage-dividers 61 are connected between bus lines69 and II supplied with potential from a secondary section 13 of thepowersupply transformer ll. Each of the pre-set terminal tap I of thevoltage-divider l8 and one bus-line l! is connected to its intermediatetap ll.

In the practice of my invention, the pre-setvoltage-dividers 01 areadjusted to correspond to the desired values of illumination before theperformance. During the performance. the switches I1 between onevoltage-divider l1 and the one necessary for the subsequent scene areclosed and when the transition is to occur. the

movable contact I! of the differential voltagedivider I! is shifted froma position corresponding to the first presetting to the positioncorresponding to the subsequent pre-setting.

The connection between'the pre-set voltagedivider system 65 and thevoltage-divider 48 is such that when the pre-set voltage-divider systemis supplied with power, the potential impressed through it between thecontrol electrode 3 and the cathode I is in phase with the principalpotential and, therefore, in opposite phase to the opposite-phasepotential component from the secondary section ll.

The potential supplied by the pre-set system I is represented in Fig. 3by a vector 8| parallel to the principal potential vector 5' and inphase therewith. The net potential supplied to the electric dischargedevice when power is supplied to the pre-set system 65 is represented bya dotdash vector '3 which, it will be noted, lags the principalpotential by a comparatively small angle. In consequence thereof, theoutput of the discharge device I is of considerable magnitude under suchcircumstances.

It is seen that as the adjustments of the prepotentiometer 61' arevaried and as the movable contact I! of the diflerential voltage-dividerI5 is shifted. the parallel vectors 5! and BI inFig. 3 may be variedfrom one magnitude in the opposite phase position to another magnitudein the in-phase position and as this variation takes place, the phase ofthe control potential relative to the principal potential is varied. Itis apparent also that by adjusting one or the other of the movable taps49 and BI associated with the voltage-divider 43, the relationshipbetween the vectors 51 and ll may be adjusted and varied in any desiredmanner, and consequently the range covered by the system may be varied.The voltage-divider 43 is utilized to provide the adjustments formaximum and minimum output of the system, the contact 5| being set toprovide the desired maximum adjustment and the contact "being set toprovide the desired minimum adjustment. The output of the system may bevaried from the desired minimum to the desired maximum by varying thevoltage-dividers 65 and I! of the pre-set system 65. In certainmodifications of my invention it is possible to replace thevoltage-divider l3 entirely by the variable resistor II. I

To protect the cathode "I of the discharge device I from deterioration,I provide a time delay relay 8! the movable contactor 81 of which isoperated a predetermined interval of time after the main switch (notshown) is closed. The interval of time is suflicient to enable thecathode of the electric discharge device to attain the propertemperature of emission.

. Whenthesystemisnotinusethemovablecontactorfloftherelaytlisdisensaled'fromita correspondingnxedcontactsllandthebusline ll'inwhich'thecontactellareinsertedismaintained open. Thepro-set voltage divider system I is therefore deenergised. when the mainswitchiscloeed theapparatusissuppliedwith power but the relay It doesnot operate until the predetermined interval of time has elapsed. Duringthe interval, the control potential supplied to the discharge device isin the condition represented by'the broken line vector I substantiallyin opposite phase to the principal potential and the cathode isprotected from deterioration.

when the relay is eventually operated, the proper potential is suppliedto the discharge device to energize it in' the manner explained above.

. In Fig. 2, a phase shifting system is shown.

The phase shifting system may be utilized as the phase shifter 83 in theapparatus shown in Fig. l, or it may and preferably is utilized in placeof the complete system whereby control potential is provided. In Fig. 2,the system is shown coupled to a discharge device I as it would inapparatus in which it completely replaces the control po-,- tentialsupply system shown in Fig; 1.

The apparatus shown in Fig. 2 comprises a network OI consisting of aresistor Cl and a reactor 96 connected in series with .each other. Thereactor 95 is preferably, as shown, an inductor.' However, it may be acapacitor. The principal feature which is desired of the impedances ofthe network is that they be of a type such that when an alternatingpotential is applied across the network, the current transmitted throughone of the impedances is in quadrature with the-current transmittedthrough the other.

An alternating potential is supplied to the network III from thesecondary lI-of a transformer 99 the terminal taps IIII and III! ofwhich are connected to the terminals of the network. A plurality ofpre-set voltage-dividers I05 are connected in parallel with the network9| across the secondary, the terminal taps I01 and III! of thevoltage-dividers being connected to the terminal taps III and I03 01 thesecondary. The voltagedividers I05 are provided with an intermediate tapIII and the intermediate tap is connected to the junction point H3 ofthe reactor 95, and the resistor '83. In certain modifications of myinvention the intermediate tap III is connected to some pointintermediate the terminals of the network SI rather than to the junctionpoint I I3. As in the apparatus shown in Fig. l the diflerentialvoltage-divider It is coupled to the pre-set voltage-dividers I05through switches 11 in the usual manner.

The secondary 9I is provided with an intermediate tap I I5 and it isconnected to the anode 5 of the discharge device I to be controlled. Thecontrol electrode 3 of the discharge device is connected to the movablecontact IQ of the differential potentiometer 15. v I

The functioning of the system is illustrated in Fig. 4 vectorially. Thehorizontal vector II'I represents the potential supplied by thesecondary 91, the intermediate tap H5 or its electrical equivalent theanode 5 being represented by a point IIS intermediate the ends of thevector.

The potential impressed across the resistor 93 III is the diameter. Theresistor vector I2I lags in phase behind the reactor vector I23.

Consider any one of the pre-set voltage-dividers I05 as its movablecontact element I21 is displaced from its upper terminal I 91 to itsintermediate tap III. Under such circumstances, the potentials of themovable contact I21 correspond to the potentials of points along theresistor 99.

As the movable contact I21 is displaced from the upper terminal I91 01'the voltage-divider III5 to the intermediate tap III, the potentialimpressed between the movable contact I21 and the intermediate terminalIll 01' the secondary 91 or between the-anode 5 and the controlelectrode 9 oi. the discharge device I may be represented by a vectorI29 one terminal of which is at the point correspondingto theintermediate tap H5 oi the secondary 91 and the other terminal'ot whichlies on the resistor vector I2I. The vector I29 varies from a positionin which it corresponds to the electrical potential between theintermediate tap II5 to the upper terminal III of the secondary 91 to aposition in which it corresponds to the electrical potential between theintermediate tap I I5 and the junction point H3 01' the impedances 93and 95.

Again, as the movable contact I21 of the voltage-divider I 05 moves fromthe intermediate tap III to the lower terminal I09 the potentialimpressed between thevmovable contact I21 and the intermediate tap I I501 the secondary 91 corresponds to points along the inductor 95 and maybe represented by a vector I3 I which extends from the point II9representing the intermediate tap I I5 oi the secondary 91 to pointsalong the vector I23 representing the inductor potential. The vector Illrotates from the intersection point I33 of the resistor and inductorvectors I2I and I23 to coincide with the vector II1 representing thesecondary potential. It is seen that as the movable contact I21 of thepre-set voltage-dividers I05 are varied, the potential impressed betweenthe intermediate tap I I5 oi the secondary 91, and the movable taps I21that is, substantially between the anode 5 and the control electrode 3of the discharge device I may be varied through a full angle of 180". Inpractice, the movable contact elements I21 oi the pre-setvoltage-dividers I 95 are adjusted before the performance and theadjustment during the performance is made by the movable contact of thediflerential voltage-divider 15.

Although I have shown and described certain specific embodiments 01 myinvention, I am fully aware that many modifications thereof arepossible. My invention, therefore, is not to be restricted exceptinsofar as is necessitated by the prior art and by the spirit of theappended claims.

I claim as my invention:

'1. Translating apparatus comprising an elec-' tric discharge devicehaving a control electrode and a plurality of principal electrodes,means for applying a periodic principal potential on said electricdischarge device, means for applying a periodic control potential onsaid electric discharge device that is composed ot a component which maybe represented by a vector parallel to the vector representing theprincipal potential and a component which may be represented by a vectorat an angle less than 180 to the vector representing the principalpotential and means for varying the first said component continuouslyfrom a predetermined magnitude in opposite phase to the principalpotential to a predeterphase with the principal on said discharge devicethat is composed of acomponent which may be represented by a vectorparallel to the vector representing the principal potential and acomponent which may be represented by a vector at an angle les than tothe vector representing the pri:.-cipal potential and means for varyingthe first said component continuously from a predetermined magnitude inopposite phase to the principal potential to a predetermined magnitudein' phase with the principal potential.

3. Translating apparatus comprising an electric discharge device havinga control electrode and a plurality of principal electrodes, means forapplying a principal potential on said electric discharge device, meansfor applying a control potential on said electric discharge device thatis composed of a component which may be represented by a vector parallelto the vector representing the principal potential and a component thatmay be represented by a vector at an angle less than 180 to the vectorrepresenting the princlpal potcntial and means for varying the first sald components continuously from a predetermined magnitude in oppositephase to the principal potential to a predetermined magnitude in phasewith the principal potential, the last said means including a pluralityof pre-set voltage-dividers and means for continuously varying thevoltage-divider output from that corresponding to one of said settingsto that corresponding to another of said settings.

4. Translating apparatus comprising an elec tric discharge device havinga control electrode and aplurality of principal electrodes, means forapplying a principal potential to said electric discharge device, meansfor applying a component oi control potential to said electric dischargethat may be represented by a vector at an angle lws than 180 to thevector representing said principal potential, means for applying acomponent of control potential to said discharge device that may berepresented by a vector parallel to the vector representing theprincipal potential, a plurality of pre-set voltage-dividers and meansfor continuously varying the last said component of control potentialfrom a value corresponding to one of said voltage-divider settings to avalue corresponding to another of said voltagedivider settings.

5. Translating apparatus comprising an electric discharge'device havinga control electrode and a plurality of principal electrodes, means forimpressing a principal potential on said electric discharge device,means for impressing a component of control potential-on said dischargedevice that differs in phase from said principal potential by an angledifferent from 180, means for impressing a component of. controlpotential on said discharge device that is in opposite phase ponent apredetermined interval of time after the opposite-phase component hasbeen applied.

6. Translating apparatus comprising an electric discharge device havinga control electrode, an anode and a hot cathode, said cathode being ofthe type that deteriorates if principal potential is applied in suchmanner as to render said discharge device conductive before the cathodeis heated to a predetermined temperature, means for impressing aprincipal potential on said electric discharge device, means forimpressing a potential to heat said cathode, means for impressing acomponent of control potential on said discharge device that differs inphase from said principal potential by an angle different from 180,means for impressing a component of control potential on said dischargedevice that is in opposite phase to said principal potential, means forsuperposing on the last said component a component that is in phase withsaid principal potential, and means for delaying the application of thelast said component a predetermined interval of time after the oppositephase component, the principal potential and the heating potential havebeen applied.

'7. Translating apparatus comprising an electric discharge device havinga control electrode and a plurality of principal electrodes, means forimpressing a periodic principal potential on said electric dischargedevice, means for impressing a component of control potential on saiddischarge device that is periodic and differs in phase from saidprincipal potential by an angle difierent from 180, means for impressinga component of control potential on said discharge device that isperiodic and in opposite phase to said principal potential, means forsuperposing on the last said component a component that is in phase withsaid principal potential and means for varying the magnitude of the lastsaid components from one predetermined value to another.

8. A phase-shifting system comprising a source for applying analternating potential, a resistance and a reactance connected in serieswith each other across said source, a voltage-divider having anintermediate tap, means for connecting said voltage-divider across saidsource in parallel with said resistance and reactance, means forconnecting said intermediate tap to the junction point of said reactorand said resistor, a plurality of terminals upon which a desired dif-Ierence of potential is to be impressed, means for connecting one oi.said terminals to an intermediate point on said voltage divider andmeans for connecting another of said terminals to a point on saidsource.

9. A phase-shitting system comprising a network consisting of twoimpedances connected in series, said impedances being of a type suchthat when an alternating potential is impressed across said network, thepotential impressed across one of said impedances is in quadrature withthe potential impressed across the other, means for impressing analternating potential across said network, a voltage-divider having anintermediate tap, means for connecting said voltage-divider in parallelwith said network, means for connecting said intermediate tap to saidnetwork at a point intermediate the terminals thereof, a plurality ofterminals upon which a desired difierence of potential is to beimpressed, means for connecting one of said terminals to an intermediatepoint on said voltage-divider and means for connecting another of saidterminals to a point on said means whereby alternating potential isimpressed across said network.

10. In combination,-an electric discharge device having a controlelectrode and a plurality of principal electrodes, means for impressinga principal potential on said electric discharge device, a networkconsisting of a resistor and a reactor connected in series with eachother, means for impressing an alternating'potential across theterminals of said network, a voltage-divider having an intermediate tapand a movable contact, means for connecting said voltage-divider inparallel with said network, means for connecting the intermediate tap ofsaid voltage-divider to an intermediate point on said network, means forconnecting the anode of said electric discharge device to a point onsaid means whereby potential is supplied to said network and means forconnecting the movable contactor of said voltagedivider to said controlelectrode.

11. Translating apparatus comprising an electric discharge device havinga control electrode and a plurality of principal electrodes, means forimpressing a periodic principal potential on said discharge device,means for impressing a periodic control potential on said dischargedevice, said control potential consisting of a component out of phasewith said principal potential by an angle diilerent from 180", acomponent in opposite phase to said principal potential, saidopposite-phase component being adjusted to a magnitude such that when italone is applied the output of'said discharge device is at the desiredminimum, a component in phase with the principal potential, saidin-phase component being adjusted to a maximum magnitude such that whensaid maximum magnitude is superposed on the opposite-phase component,the output of said discharge device is the desired maximum and means forvarying said in-phase component from zero to its maximum magnitude.

JOHN W. DAWSON.

